June 26, 2012

Cascade Melt Out

There are few more important questions for Northwest hikers:  when will their favorite trails melt out and the hiking season begin in earnest?  

And few more important questions for those concerned about the local impacta of global warming:  is the Cascade snowpack melting out earlier, thus providing evidence of the effects of increasing greenhouse gases in the atmosphere. 

This truth may surprise some and depress others.  

It turns out that the Cascade snowpack has been trending to melt out LATER during the past thirty years, with the last few years being particularly late.  For example, Stevens Pass finally melted out yesterday--3 weeks later than normal.

Here is a plot of the melt-out date at Stevens Pass from 1981 through this year (courtesy of UW atmospheric scientist Mark Albright).  The y axis shows the melt-out day (days into the year) and the purple line shows a 5-year running average.  The overall trend is clearly for a later melt out.
The mean melt-out dates by decade illustrate this trend:

1980s:  30 May
1990s:  1 June
2000s:  2 June
2003-12:  6 June

Three of the five latest melt-out dates have been during the past five years:

1 July 2011 THE LATEST!
25 June 2008
25 June 1999
24 June 2012
23 June 1997

Paralleling the late snowpack melt-out is the April 1 snowpack amount, which has not shown any decline over the past 30 years.

Does this trend in snow melt out  mean that the Northwest does not have to worry about greenhouse warming? The answer is no.  By the middle of this century the Northwest snowpack should clearly be on decline as the earth warms, but as I have mentioned many times in this blog, the entire world will not warm at the same rate.  Downstream of the eastern Pacific, the coastal portions of the Pacific Northwest (Cascade crest westward) will warm up more slowly than most places, since the eastern Pacific will take its time to heat up.

Let me illustrate this.  Here is the change in global temperature from 1980 through this year for the winter months (courtesy of Goddard Institute for Space Studies).  The eastern Pacific has COOLED, and we have cooled with it.  But we are the exceptions...most of the earth has warmed and the arctic region has really warmed.   So there is global warming (with some contribution from man-caused increasing greenhouse gases), but out neighborhood has cooled...temporarily.

Pretty interesting stuff and with important implications for us here in the NW...we have much more time than most to prepare for the effects of global warming.....at least the temperature/snow part of the changes. So if someone tries to tell you that the coastal NW has already experienced major effects due to global warming, you might question their information.   And if someone says that a stable or increasing snowpack the past few decades proves global warming is nonsense...I would not trust their information either.  


  1. Cliff,
    Even if it melts out later, is there any merit to the idea that the summers are warmer, thus causing further reduction in glacier size?
    Is the reduced size and disappearance of at least 2 glaciers in the N Cascades more a harbinger of global warming trends or merely the last vestiges of the last ice age?

  2. Hi Cliff,
    My non-scientific observation of the same time period (last 30 years) is that the amount of snow at the passes and up high may not have changed, or may even have increased, but that the snow line (elevation of consistent winter snow pack) has risen. Areas where we used to reliably X-C ski, like Foss River Road, are rarely covered. So my (again non-scientific) conslusion has been that temps have warmed enough to raised the snow level while percipitation has remained consistent (or increased) thus ensuing plenty of snow above a certain elevation, but that the overall volume of snow is less. Am I wrong about this?

  3. Just for fun, related, ...


  4. Cliff: The GCM runs for the Northwest did not forecast cooling. They were forecasting a steady but slow warming of approxiamtely 1 degF per decade. I know because I have Phil Mote's papers from Climate Impacts Group and copies of his model simulations.

    So why would GCM's continue to flounder predicting warming ( which they are still doing) and you are now backing way off and calling for a warming from greenhouse gases that won't really be verifiable until the middle of this century when you and I and most others reading this will be dead?

    What is your scientific justification of this? And if CO2 emissions are causing warming, why has the entire USA been cooling for the last 14 years, and apparently joining the cooling trend of the Northwest? Have we had a permanent trough located on the west coast? I think not!Atmospheric CO2 everywhere has gone up 53.9 ppmv since 1980. What you say makes no sense to me.

  5. Unknown,
    The GCMs do show this general pattern..arctic warms up the most, continents more than oceans, eastern oceans less than western oceans.....cliff

  6. Depressing is all I can say. I am sure many natives will take issue with me but if anyplace needs some global warming, it's here. At least enough to banish the June Gloom. Every June I get envious of the rest of the country because THEY are already into summer.

    If only we could trade weather with Colorado. I am sure they too would be grateful right now.


  7. But GCM's fail the reality test in that Random Walks often come up with the same results. I think that any certainty to the statment that there will be a warming within 50 years is rubbish. We simply don't have that kind of accuracy, and certainly not with the GCMs. Climate is far more complex than many who profit from it are willing to admit.

  8. looks like melt out date is almost perfectly negatively correlated with the PDO index

  9. Those who profit? Like say, the oil industry? Talk about a ridiculous argument.

    George W. Bush and John McCain have admitted that climate change is happening.

    Stop sucking up to Russia, Iran, Saudi Arabia, Venezuela, and the other oil producers. Support natural gas, support nuclear, and support alternate energy.

  10. An environmental group stopped by my house recently with a flier and then a knock on the door. Their pitch was "Have you notcied all the crazy weather around here lately? It's global warming!" I kept the flier and can scan it in if you're interested though I expect you've seen plenty of this stuff before.

  11. Ben...yes...I would be interested in seeing a scan of it...thanks, cliff

  12. Cliff, I work on a Forest Service trail crew out of Cle Elum. Melt-out is definitely behind this year. We went to Waptus Lake this past week (in the rain) and there are still 3.5' deep snowdrifts. A person could ski back there. Folks wanting to hike in the Cascades can go anywhere they want, but they may be on snow rather than dirt. We're not funded to shovel out the Pacific Crest Trail. Would love to go to a fire in Colorado just to dry out my boots...


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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